Browser extensions and add-ons

Each of the main browsers on the market has the capability to add in extra features and functions through the form of add-ons (sometimes known as extensions or plugins).

When you are testing your website you'll want to take advantage of these. I’ve included some of my favourites here but go exploring, new ones are being added every day.

(Note: the URLs sometimes changes and some of these extensions come and go. If the link doesn’t work a quick search should find it)

Selenium IDE

Selenium is fast becoming an industry standard tool. This is the IDE version. Visit for more information on other tools in the set like Selenium Grid.

IE Tab
Flips your Firefox tab in to Internet Explorer mode.

Re-sizes your window to different screen sizes

Fire cookie

Lets you to see and manage cookies through the Firebug add-on.

Clear Cache

Clears out the cache within the browser at the click of a button.

Copy Plain Text

Copies any text from the browser in to a plain text format losing all formatting.

Download Status

Shows your downloads in a toolbar at the bottom of the browser window. Keeps it nice and tidy and easy access to your downloads.


Allow you to save your bookmarks and sync them between browsers on different machines. Works across browsers too. This is great if you test on several different machines. It means you can save your bookmarks once and find them on other browsers you have synched.

W3C Page Validator

Check your page against W3C standards and compliance.


Great for screen mocks and notes.

SQL Injection

Does exactly as the name suggests

Quick Restart

Restarts Firefox maintaining all tabs and open docs when it launches it again.


How can you test websites without this one?

Regular Expressions Tester

Tool for testing regular expressions.

Quick Locale Switcher

Good extension allowing for quick switching between browser locales.

Http Fox

Good tool for analyzing the http traffic through your browser.


Accessibility checking tool. Awesome.

Firefox Accessibility Tools

Accessibility compliance checking tool.

This is barely scratching the surface but you can already start to imagine how useful some of these would be for testing your website. Add-ons allow you to be more efficient with your time, perform tests you might normally not be able to and allow you to let the tools do the hard work.

These are obviously for Firefox, but some of these also exist for Chrome and other browsers.

How to install them

Open Firefox > Tools > Add-ons > Extensions and then search for, and download each add-on. (or copy and paste the links above)

Each tool will work in different ways but the documentation on the site is normally pretty good.

Useful Hint

Sometimes the extensions themselves can cause issues. I've seen this a couple of times where a problem with a website goes away when the extensions are removed.

Useful Links

Main extensions website for Firefox

Chrome extensions

Opera extensions

Safari extensions

Cool hacks to Firefox like making it quicker

Here’s some more on - hat-tip to @dannydainton for the link .


If you’re interested in a career in Software Testing then check out my book Remaining Relevant And Employable (Tester’s Edition) - it’s packed full of ideas about writing good CVs, communicating your value to employers and doing well in an interview.